Combustion safety control system



Nov. 28, 1950 H. G. NEHRBAs i 2,531,887

COMBUSTION SAFETY CONTROL SYSTEM Filed Dec. 2, 1947 HOW/WD G. IVE/maas wsa/roe.

Patented Nov. 28, 1950 COMBUSTION SAFETY CONTROL SYSTEM.

Howard G. Nehrbas, Hammond, 1nd., assigner to Combustion Engineering-Superheater, Inc., a

corporation of Delaware Application December 2, 1947, Serial No. 789,234

1 Claim.

The present invention relates to improved means for actuating a signal or shutting ofi the supply of fuel to a furnace in the event that the lire goes out.

The invention is particularly adapted for use with burner fired boilers and provides for cutting off the supply of pulverized coal, gas or oil to the burners in case the fuel fails to ignite or the flame dies out. The present invention contemplates accomplishing this by continuously withdrawing a small amount of combustion gases from the furnace and passing them over thermally responsive elements that may actuate a signal or the combustion controls. The invention will be best understood upon consideration of the following detailed description of an illustrative embodiment thereof when read in conjunction with.l the accompanying drawings in which the single figure is a diagrammatic View of a furnace system embodying electrical means that is actuated in the event the nre goes out.

Referring to the drawing, the furnace designated as a whole by the numeral I is fed by a burner II which introduces fuel oil into the furnace from one end thereof while the products of combustion flow out of the furnace, `and eventually to a stack, through an outlet at the lower end of the furnace. Closely adjacent the burner II, or at least within the limits of the zone of combustion in the furnace, an orifice I2 is formed in the furnace wall to which is connected aconduit I3 leading to a discharge outlet or stack I4. Disposed in the conduit I3 in the path of hot gases flowing from the furnace to the outlet Ill is a thermally responsive element I5. This element I5 may be made of a composition that has a very high negative co-efcient of electrical resistivity with respect to temperature so that when the material is heated its electrical resistance drops quite rapidly. The thermal element I5 is arranged in series with a relay IS connected through the wires I'I and I8 to an electrical power source. The armature or other switch element 20 of the relay I 6 is in turn arranged in the electrical circuit ofI electro-magnet coil 3l associated with one of the controls that regulate the combustion in the furnace. This may be an electro-magnetically operated oil valve 23 as shown by way of example in the figure. A circuit 2|, 22 including an alarm 33 and visual signal may be closed by contacts 34 on failure of the llame as switch 25 opens to stop the supply of fuel. Connected to conduit I3 is an air inlet 24 through which air is supplied by a fan 25. A damper 26 in inlet 24 is controlled by another thermally responsive element 21 located in conduit I3.

When the furnace is cold the damper 2B is closed. Upon pressing burner starting button 30 the electromagnet 3I is energized and opens oil valve 23. On lighting of the fire some of the hot gases of combustion 110W through conduit I3 to outlet I4 and passing over the element I5 cause its electrical resistance to be lowered so that sufcient current may flow through the relay coil I5 to permit switch 2i) to close and maintain the oil valve 23 open. Starting button 35 may then be released and the electromagnet held by stop switch 32 subject to switch 25. The temperature responsive element 21 in conduit I3 is also heated by the gases and operates damper 26 to maintain a predetermined constant temperature of gases flowing over the control element I5. If the re should go out the temperature of element I5 drops and its electrical resistance rises reducing the current through relay I6 so that this relay is released. This may result in operating an alarm such as alarm 33 through contacts 34 and/or break the burner control circuits, as shown at 23, to stop the supply of fuel to the furnace.

The special thermally resistant element I5 in the control circuit for the alarm or burner control may be replaced by an ordinary type of thermally responsive switch adapted to maintain 1its contacts engaged when the burner is in operaion.

What I claim is:

In combination with a furnace chamber having means for introducing fuel into the latter for combustion therein; a conduit in communication with the interior of said furnace connected thereto immediately adjacent the zone of combustion for withdrawing hot gases of combustion from the furnace; electrical means associated with said furnace for controlling the supply of fuel to said furnace; thermally responsive circuit control means disposed in said conduit for exposure to gases of combustion withdrawn from the furnace and so connected as to cause actuation of said electric means upon failure of combustion therein; blower means connected to said conduit at a point between said furnace and said thermal means for supplying air to said conduit for mixture with the gases flowing therethrough; damper means for regulating the supply of air to said conduit by said blower means; and other thermally responsive means located in said conduit at a point intermediate said first thermally responsive means and said blower means and controlling said damper means to maintain a predetermined temperature of the mixture of gas and air iiowing over said first thermally responsive means.

HOWARD G. NEHRBAS.

REFERENCES CITED The following references are of record in the le of this patent:

UNrrED STATES PA'I'ENTS 

